Refrigeration device

Abstract

Provided is a refrigeration device capable of reliably performing refrigerant recovery after stopping a heating operation. This refrigeration device executes a heating operation. The refrigeration device comprises a refrigerant circuit, a heat source fan, and a control unit. The refrigerant circuit has a compressor and a heat source heat exchanger. The heat source fan supplies air to the heat source heat exchanger. The control unit controls the compressor and the heat source fan. Upon detecting an instruction to stop the heating operation, the control unit drives the heat source fan while keeping the compressor stopped, and starts a first operation for recovering refrigerant to the compressor or the heat source heat exchanger. The control unit stops the heat source fan and ends the first operation when an end condition that refrigerant in the refrigerant circuit is in a predetermined state is satisfied.

Description

Refrigeration equipment

[0001] Regarding refrigeration equipment.

[0002] Patent Document 1 (JP 2000-28210 A) discloses an air conditioner that performs a refrigerant recovery operation, utilizing the temperature difference between indoors and outdoors to recover refrigerant to the outdoor unit after operation has been stopped, in order to reduce the risk of refrigerant leakage.

[0003] In Patent Document 1, the conditions for ending the refrigerant recovery operation are unclear. Therefore, in the air conditioner of Patent Document 1, there is a risk that the refrigerant recovery operation will end in a state where refrigerant remains in the indoor unit and the refrigerant has not been recovered, resulting in incomplete refrigerant recovery.

[0004] An object of the present disclosure is to provide a refrigeration apparatus that can reliably recover refrigerant after heating operation is stopped.

[0005] A refrigeration device according to a first aspect performs a heating operation. The refrigeration device includes a refrigerant circuit, a heat source fan, and a control unit. The refrigerant circuit has a compressor and a heat source heat exchanger. The heat source fan supplies air to the heat source heat exchanger. The control unit controls the compressor and the heat source fan. When the control unit detects an instruction to stop the heating operation, it starts a first operation in which it drives the heat source fan while keeping the compressor stopped, and recovers refrigerant to the compressor or the heat source heat exchanger. When an end condition is met in which the refrigerant is in a predetermined state in the refrigerant circuit, the control unit stops the heat source fan and ends the first operation.

[0006] By driving the heat source fan and supplying air to the heat source heat exchanger, the refrigerant in the heat source heat exchanger is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit is recovered from the utilization unit side, where the pressure is relatively high, to the heat source heat exchanger. Furthermore, the heat source fan is stopped and the first operation, which is the refrigerant recovery operation, is terminated after a termination condition is met in which the refrigerant in the refrigerant circuit is in a predetermined state. This prevents the first operation from being terminated before the refrigerant recovery is fully completed. Therefore, this refrigeration system can reliably recover refrigerant after operation is stopped.

[0007] A refrigeration apparatus according to a second aspect is the refrigeration apparatus according to the first aspect, wherein the termination condition is a state in which the pressure of the refrigerant in the refrigerant circuit is equal to or lower than a predetermined first pressure, or the temperature of the refrigerant in the refrigerant circuit is equal to or lower than a predetermined first temperature.

[0008] The present refrigeration system determines the state of refrigerant recovery based on the pressure or temperature of the refrigerant in the refrigerant circuit, and therefore can reliably recover refrigerant after operation has been stopped.

[0009] A refrigeration apparatus of a third aspect is the refrigeration apparatus of the second aspect, wherein the termination condition is a state in which the pressure of the refrigerant in the gas pipe of the refrigerant circuit is equal to or less than a first pressure, or the temperature of the refrigerant in the gas pipe of the refrigerant circuit is equal to or less than a predetermined first temperature.

[0010] The present refrigeration system determines the state of refrigerant recovery based on the pressure or temperature of the refrigerant in the refrigerant circuit, and therefore can reliably recover refrigerant after operation has been stopped.

[0011] A refrigeration apparatus according to a fourth aspect is the refrigeration apparatus according to the second or third aspect, wherein the first temperature is equal to or lower than an outside air temperature.

[0012] The present refrigeration system determines the state of refrigerant recovery based on the temperature of the refrigerant in the refrigerant circuit, and therefore can reliably recover refrigerant after operation has been stopped.

[0013] A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to the second or third aspect, wherein the first pressure is a pressure of the refrigerant when the outside air temperature is an evaporation temperature.

[0014] The present refrigeration system determines the state of refrigerant recovery based on the pressure of the refrigerant in the refrigerant circuit, and therefore can reliably recover refrigerant after operation has been stopped.

[0015] A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to any one of the first aspect to the fifth aspect, wherein the control unit, in the first operation, rotates the heat source fan at a rotation speed equal to or higher than the minimum rotation speed in the heating operation.

[0016] Since the heat source fan is rotated at a speed equal to or higher than the minimum speed during heating operation, condensation of the refrigerant is promoted. Therefore, the refrigeration apparatus of this invention can reliably recover the refrigerant after operation is stopped.

[0017] A seventh aspect of the present invention is the refrigeration apparatus of any one of the first to sixth aspects, wherein the refrigerant circuit further includes an expansion mechanism, and the control unit fully opens the expansion mechanism in the first operation.

[0018] Since the expansion mechanism is fully opened, the expansion mechanism is prevented from blocking the flow of refrigerant from the utilization unit to the heat source heat exchanger. Therefore, the refrigeration apparatus can reliably recover refrigerant after operation is stopped.

[0019] A refrigeration apparatus according to an eighth aspect is any one of the refrigeration apparatuses according to the first aspect to the seventh aspect, wherein when the control unit detects an end condition in the first operation, the control unit stops the heat source fan after a predetermined time has elapsed.

[0020] Since the heat source fan continues to be driven even after the end condition is detected, the present refrigeration apparatus can reliably recover refrigerant after operation is stopped.

[0021] A ninth aspect of the present invention is the refrigeration apparatus of any one of the first to eighth aspects, wherein the refrigerant circuit further includes a shutoff valve, and the control unit closes the gas-side shutoff valve before stopping the heat source fan in the first operation.

[0022] As a result, even if the temperature difference between the refrigerant in the utilization heat exchanger and the refrigerant in the heat source heat exchanger becomes smaller after the first operation due to a drop in the temperature of the space to be air-conditioned, the refrigeration device can prevent the refrigerant recovered in the heat source heat exchanger from returning to the utilization unit.

[0023] A refrigeration apparatus according to a tenth aspect is the refrigeration apparatus according to the ninth aspect, wherein the control unit closes the gas-side shutoff valve after detecting a termination condition in the first operation.

[0024] This prevents the refrigerant recovered in the heat source heat exchanger from returning to the utilization unit, even if the temperature difference between the refrigerant in the utilization heat exchanger and the refrigerant in the heat source heat exchanger becomes small after the first operation due to a drop in the temperature of the space to be air-conditioned, etc.

[0025] The refrigeration device of the eleventh aspect is any one of the refrigeration devices of the first aspect to the tenth aspect, in which the instruction to stop heating operation is output due to the room temperature approaching the set temperature during heating operation.

[0026] A twelfth aspect of the present invention is the refrigeration apparatus of any one of the first aspect to the eleventh aspect, wherein the refrigerant is a flammable refrigerant.

[0027] This prevents the flammable refrigerant from leaking into the space to be air-conditioned after the refrigeration apparatus has stopped.

[0028] It is a schematic configuration diagram of a refrigeration device 100 according to an embodiment of the present disclosure. It is a block diagram of a control unit 60. It is a flowchart showing a control flow of a refrigerant recovery operation executed by the control unit 60. It is a time chart showing the operation of each part in the refrigerant recovery operation.

[0029] <Embodiment> (1) Overall Configuration Fig. 1 is a schematic configuration diagram of a refrigeration apparatus 100 according to one embodiment of the present disclosure. The refrigeration apparatus 100 performs air conditioning operation of a space to be air-conditioned (not shown) by performing a vapor compression refrigeration cycle operation in a refrigerant circuit 10. The air conditioning operation includes a cooling operation and a heating operation. In addition, as will be described in detail later, the refrigeration apparatus 100 performs a refrigerant recovery operation. The refrigeration apparatus 100 mainly includes one heat source unit 20, one utilization unit 50, a liquid refrigerant communication pipe 2, a gas refrigerant communication pipe 4, and a control unit 60.

[0030] The refrigerant circuit 10 is configured by connecting each device of the heat source unit 20 and the user units 50 via refrigerant piping to the liquid refrigerant communication pipe 2 and the gas refrigerant communication pipe 4. More specifically, the refrigerant circuit 10 includes a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion mechanism 24, a shutoff valve 29, a user heat exchanger 51, the liquid refrigerant communication pipe 2, and the gas refrigerant communication pipe 4, which are connected via refrigerant piping. A refrigerant is sealed in the refrigerant circuit 10. The refrigerant sealed in the refrigerant circuit 10 is a flammable refrigerant such as propane.

[0031] (2) Detailed Configuration (2-1) Usage Unit 50 The usage unit 50 has a usage heat exchanger 51 and a usage fan 52. The usage unit 50 is installed, for example, in a space to be air-conditioned.

[0032] (2-1-1) Utilization Heat Exchanger 51 The utilization heat exchanger 51 exchanges heat between the refrigerant flowing inside and the air in the space to be air-conditioned. The utilization heat exchanger 51 has a liquid side end 51a and a gas side end 51b.

[0033] The liquid side end 51a is connected to the liquid refrigerant communication pipe 2 via a refrigerant pipe. The gas side end 51b is connected to the gas refrigerant communication pipe 4 via a refrigerant pipe.

[0034] (2-1-2) Usage Fan 52 The usage fan 52 supplies air to the usage heat exchanger 51. The usage fan 52 is driven by a motor 52a. The rotation speed of the motor 52a is controlled by the control unit 60.

[0035] (2-2) Heat Source Unit 20 The heat source unit 20 has a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion mechanism 24, an accumulator 25, a shut-off valve 26, a heat source fan 27, a pressure sensor 28, and a shut-off valve 29. The heat source unit 20 is disposed, for example, outside the space to be air-conditioned.

[0036] (2-2-1) Compressor 21 The compressor 21 draws in low-pressure refrigerant in the refrigeration cycle through a suction pipe 21a, compresses the refrigerant using a compression mechanism (not shown), and discharges the refrigerant to a discharge pipe 21b as high-pressure refrigerant in the refrigeration cycle. The capacity of the compressor 21 is controlled by the control unit 60. The operating capacity of the compressor 21 is controlled by controlling the rotation speed of a motor (not shown) that drives the compression mechanism.

[0037] (2-2-2) Flow Direction Switching Mechanism 22 The flow direction switching mechanism 22 switches between a first state and a second state to switch the direction of refrigerant flow. The flow direction switching mechanism 22 is switched between the first state and the second state by the control unit 60. In this embodiment, the flow direction switching mechanism 22 is a four-way switching valve.

[0038] In the first state, the flow direction switching mechanism 22 connects the inlet 25a of the accumulator 25 to the gas refrigerant communication pipe 4 and connects the discharge pipe 21b of the compressor 21 to the gas side end 23b of the heat source heat exchanger 23 (see the solid line in the flow direction switching mechanism 22 in FIG. 1 ). In the second state, the flow direction switching mechanism 22 connects the inlet 25a of the accumulator 25 to the gas side end 23b of the heat source heat exchanger 23 and connects the discharge pipe 21b to the gas refrigerant communication pipe 4 (see the dashed line in the flow direction switching mechanism 22 in FIG. 1 ).

[0039] (2-2-3) Heat Source Heat Exchanger 23 The heat source heat exchanger 23 exchanges heat between the refrigerant flowing therein and the air (heat source air) at the installation location of the heat source unit 20. The heat source heat exchanger 23 has a liquid side end 23a and a gas side end 23b.

[0040] The liquid side end 23a is connected to the liquid refrigerant communication pipe 2 via a refrigerant pipe. The gas side end 23b is connected to the gas refrigerant communication pipe 4 via a refrigerant pipe.

[0041] (2-2-4) Expansion mechanism 24 The expansion mechanism 24 adjusts the pressure and / or flow rate of the refrigerant flowing through the refrigerant circuit 10. The expansion mechanism 24 is provided in the refrigerant piping that connects the liquid refrigerant communication piping 2 and the liquid side end 23a of the heat source heat exchanger 23. The expansion mechanism 24 is an electric expansion valve whose opening degree is variable and which can be fully closed. The opening degree of the expansion mechanism 24 is controlled by the control unit 60.

[0042] (2-2-5) Accumulator 25 The accumulator 25 separates the inflowing refrigerant into gas refrigerant and liquid refrigerant. The accumulator 25 also stores therein excess refrigerant that occurs in response to fluctuations in the operating load of the utilization unit 50. The accumulator 25 has an inlet 25a and an outlet 25b.

[0043] The inlet 25a is connected to the flow direction switching mechanism 22. The outlet 25b is connected to the intake pipe 21a of the compressor 21.

[0044] (2-2-6) Shut-off valve 26 The shut-off valve 26 shuts off the flow of refrigerant through the refrigerant pipe when it is in a closed state. The shut-off valve 26 includes a liquid-side shut-off valve 26a and a gas-side shut-off valve 26b. The shut-off valve 26 is, for example, a valve that is manually operated.

[0045] The liquid-side shutoff valve 26 a is provided in the refrigerant piping that connects the liquid-side end 23 a of the heat-source heat exchanger 23 and the liquid refrigerant junction piping 2 , between the expansion mechanism 24 and the liquid refrigerant junction piping 2 .

[0046] The gas-side shutoff valve 26 b is provided in the refrigerant pipe that connects the flow direction switching mechanism 22 and the gas refrigerant communication pipe 4 .

[0047] (2-2-7) Heat Source Fan 27 The heat source fan 27 supplies air to the heat source heat exchanger 23. The heat source fan 27 is driven by a motor 27a. The rotation speed of the motor 27a is controlled by the control unit 60.

[0048] (2-2-8) Pressure Sensor 28 The pressure sensor 28 detects the pressure P of the refrigerant in the refrigerant circuit 10. The pressure sensor 28 is provided on the refrigerant pipe connecting the gas side shut-off valve 26b and the gas refrigerant communication pipe 4. In this way, the pressure sensor 28 detects the pressure of the refrigerant in the gas pipe 10a of the refrigerant circuit 10 (the refrigerant pipe connecting the flow direction switching mechanism 22 and the gas refrigerant communication pipe 4).

[0049] The control unit 60 receives the pressure detected by the pressure sensor 28 .

[0050] (2-2-9) Shut-off valve 29 The shut-off valve 29 shuts off the flow of refrigerant through the refrigerant piping when it is closed. The shut-off valve 29 is provided on the refrigerant piping connecting the gas side shut-off valve 26b and the gas refrigerant communication piping 4, between the gas side shut-off valve 26b and the pressure sensor 28.

[0051] The shutoff valve 29 is controlled to open and close by the control unit 60. Specifically, the shutoff valve 29 is controlled to open during cooling operation and heating operation, and is controlled to close during a refrigerant recovery operation (to be described later) and while the refrigeration apparatus 100 is not operating.

[0052] (2-3) Liquid Refrigerant Communication Pipe 2 and Gas Refrigerant Communication Pipe 4 The liquid refrigerant communication pipe 2 and the gas refrigerant communication pipe 4 are pipes that connect the heat source unit 20 and the utilization units 50.

[0053] (2-4) Control Unit The control unit 60 controls the operation of each device in the heat source unit 20 and the utilization units 50 to realize refrigeration cycle operation and refrigerant recovery operation. FIG. 2 is a block diagram of the control unit 60. As shown in FIG. 2, the control unit 60 is electrically connected to the compressor 21, the flow direction switching mechanism 22, the expansion mechanism 24, the motor 27a of the heat source fan 27, the shut-off valve 29, and the motor 52a of the utilization fan 52 so as to be able to send and receive control signals to control the operation of these components. The control unit 60 is also electrically connected to the pressure sensor 28 so as to be able to receive pressure P. A user of the refrigeration apparatus 100 can start or end refrigeration cycle operation by instructing the control unit 60 via a remote control (not shown). The control unit 60 may be housed in either the utilization unit 50 or the heat source unit 20, or may be housed in both the utilization unit 50 and the heat source unit 20, or may be installed separately from the utilization unit 50 and the heat source unit 20.

[0054] The control unit 60 is realized by a computer. The control unit 60 includes a control and arithmetic unit and a storage device (both not shown). A processor such as a CPU or GPU can be used as the control and arithmetic unit. The control and arithmetic unit reads a program stored in the storage device and performs predetermined arithmetic processing in accordance with the program. Furthermore, the control and arithmetic unit can write the results of calculations to the storage device and read information stored in the storage device in accordance with the program. The control unit 60 may be realized by multiple computers.

[0055] (2-5) Operation of the Refrigeration System The control of the operation of the refrigeration system 100 in the cooling operation, heating operation, and refrigerant recovery operation will be described.

[0056] (2-5-1) When the air conditioning operation control unit 60 detects an instruction to start air conditioning operation sent from a remote control or the like, it sets the flow direction switching mechanism 22 to the first state and starts operating the compressor 21, the heat source fan 27, and the utilization fan 52.

[0057] The control unit 60 controls the rotation speed of the motor 27a of the heat source fan 27 and the rotation speed of the motor 52a of the utilization fan 52 to predetermined rotation speeds. For example, the control unit 60 controls the rotation speed of the motor 27a to the maximum rotation speed. The control unit 60 controls the rotation speed of the motor 52a as appropriate based on an instruction for air volume input to the remote control, etc.

[0058] The control unit 60 controls the opening degree of the expansion mechanism 24 so that the degree of superheat of the refrigerant approaches a predetermined target degree of superheat. The control unit 60 controls the operating capacity of the compressor 21 so that the evaporation temperature approaches a predetermined target evaporation temperature. The control unit 60 fully opens the shutoff valve 29.

[0059] When the compressor 21 starts operating, low-pressure gas refrigerant in the refrigeration cycle is drawn into the compressor 21 through the suction pipe 21a and compressed, becoming high-pressure gas refrigerant in the refrigeration cycle. The high-pressure gas refrigerant is discharged from the discharge pipe 21b and sent to the heat-source heat exchanger 23 via the flow direction switching mechanism 22. The refrigerant flowing into the heat-source heat exchanger 23 exchanges heat with heat-source air supplied by the heat-source fan 27, condenses, and becomes high-pressure liquid refrigerant. The high-pressure liquid refrigerant leaving the heat-source heat exchanger 23 is decompressed in the expansion mechanism 24 and becomes a two-phase gas-liquid refrigerant, and is sent to the liquid refrigerant connection pipe 2. The two-phase gas-liquid refrigerant that passes through the liquid refrigerant connection pipe 2 and flows into the utilization unit 50 is sent to the utilization heat exchanger 51. The refrigerant flowing into the utilization heat exchanger 51 exchanges heat with air in the space to be air-conditioned, which is supplied to the utilization heat exchanger 51 by the utilization fan 52, and evaporates to become low-pressure gas refrigerant. The air supplied to the utilization heat exchanger 51 is cooled by exchanging heat with the refrigerant flowing through the utilization heat exchanger 51, and then blown out into the space to be air-conditioned. The low-pressure gas refrigerant that leaves the utilization heat exchanger 51 is sent to the gas refrigerant communication pipe 4. The refrigerant that passes through the gas refrigerant communication pipe 4 and flows into the heat source unit 20 passes through the flow direction switching mechanism 22 and flows into the accumulator 25 from the inlet 25a. The low-pressure gas refrigerant that has flowed into the accumulator 25 leaves the accumulator 25 from the outlet 25b, and is then sucked into the compressor 21 again.

[0060] (2-5-2) When the heating operation control unit 60 detects an instruction to start heating operation sent from a remote control or the like, it sets the flow direction switching mechanism 22 to the second state and starts operating the compressor 21, heat source fan 27, and utilization fan 52.

[0061] The control unit 60 controls the rotation speed of the motor 27a of the heat source fan 27 and the rotation speed of the motor 52a of the utilization fan 52 to predetermined rotation speeds. For example, the control unit 60 controls the rotation speed of the motor 27a to the maximum rotation speed. The control unit 60 controls the rotation speed of the motor 52a as appropriate based on an instruction for air volume input to the remote control, etc.

[0062] The control unit 60 controls the opening degree of the expansion mechanism 24 so that the degree of subcooling of the refrigerant approaches a predetermined target degree of subcooling. The control unit 60 controls the operating capacity of the compressor 21 so that the condensing temperature approaches a predetermined target condensing temperature. The control unit 60 fully opens the shutoff valve 29.

[0063] When the compressor 21 starts operating, low-pressure gas refrigerant in the refrigeration cycle is drawn into the compressor 21 through the suction pipe 21a and compressed, becoming high-pressure gas refrigerant in the refrigeration cycle. The high-pressure gas refrigerant is discharged from the discharge pipe 21b and sent to the utilization heat exchanger 51 via the flow direction switching mechanism 22. The refrigerant that flows into the utilization heat exchanger 51 exchanges heat with air in the air-conditioned space supplied by the utilization fan 52, condensing and becoming high-pressure liquid refrigerant. The air supplied to the utilization heat exchanger 51 is heated by heat exchange with the refrigerant flowing through the utilization heat exchanger 51, and then blown into the air-conditioned space. The high-pressure liquid refrigerant that leaves the utilization heat exchanger 51 is sent to the liquid refrigerant communication pipe 2. The refrigerant that passes through the liquid refrigerant communication pipe 2 and flows into the heat source unit 20 is decompressed in the expansion mechanism 24, becoming gas-liquid two-phase refrigerant, and is sent to the heat source heat exchanger 23. The refrigerant that flows into the heat source heat exchanger 23 exchanges heat with heat source air supplied to the heat source heat exchanger 23 by the heat source fan 27, and evaporates to become low-pressure gas refrigerant. The low-pressure gas refrigerant that has left the heat source heat exchanger 23 flows into the accumulator 25 from the inlet 25a via the flow direction switching mechanism 22. The low-pressure gas refrigerant that has flowed into the accumulator 25 leaves the accumulator 25 from the outlet 25b, and is then sucked into the compressor 21 again.

[0064] (2-5-3) Refrigerant Recovery Operation (2-5-3-1) Overview The refrigerant recovery operation is an operation in which the refrigerant is recovered into the refrigerant circuit 10 on the heat source unit 20 side after detecting an instruction to stop the heating operation. Specifically, when the control unit 60 detects an instruction to stop the heating operation during the refrigerant recovery operation, it drives the heat source fan 27 while keeping the compressor 21 stopped. As a result, the refrigerant is recovered into the compressor 21 or the heat source heat exchanger 23. When an end condition is met in which the refrigerant is in a predetermined state in the refrigerant circuit 10, the control unit 60 stops the heat source fan 27 and ends the refrigerant recovery operation. The refrigerant recovery operation is an example of a first operation.

[0065] (2-5-3-2) Control Flow Fig. 3 is a flowchart showing the control flow of the refrigerant recovery operation executed by the control unit 60. Fig. 4 is a time chart showing the operation of each part during the refrigerant recovery operation. The control unit 60 starts the refrigerant recovery operation simultaneously with the start of the heating operation (start).

[0066] In step S100, the control unit 60 determines whether or not it has detected an instruction to stop the heating operation sent from a remote control or the like, and proceeds to step S100 or step S110. Specifically, if the control unit 60 detects an instruction to stop the heating operation, it proceeds to step S110 (Yes), and if it does not detect an instruction to stop the heating operation, it proceeds to step S100 (No). In other words, the control unit 60 repeats the process of step S100 until it detects an instruction to stop the heating operation.

[0067] In step S110, the control unit 60 stops the operation of the compressor 21, fully opens the expansion mechanism 24, sets the rotation speed of the motor 27a of the heat source fan 27 to a predetermined first rotation speed r1, stops the motor 52a of the utilization fan 52, and proceeds to step S120 (T1 in FIG. 4). The first rotation speed r1 may be equal to or greater than the minimum rotation speed of the motor 27a in heating operation.

[0068] By driving the motor 27a of the heat source fan 27 to supply air to the heat source heat exchanger 23, the refrigerant in the heat source heat exchanger 23 is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit 10 is recovered from the high-pressure utilization unit 50 side to the low-pressure heat source heat exchanger 23. As the recovery of the refrigerant progresses, the pressure P detected by the pressure sensor 28 (in other words, the pressure of the refrigerant in the refrigerant circuit 10) decreases over time, as shown in FIG.

[0069] In step S120, the control unit 60 determines whether the pressure P detected by the pressure sensor 28 is equal to or less than a predetermined first pressure P1, and proceeds to step S120 or step S30. Specifically, if the pressure P is equal to or less than the first pressure P1, the control unit 60 proceeds to step S120 (Yes), and if the pressure P is not equal to or less than the first pressure P1, the control unit 60 proceeds to step S130 (No). In other words, the control unit 60 repeats the process of step S120 until the pressure P becomes equal to or less than the first pressure P1.

[0070] The first pressure P1 is a pressure for determining whether a sufficient amount of refrigerant has been recovered to the heat source unit 20. The first pressure P1 is, for example, the pressure of the refrigerant when the outside air temperature is the evaporation temperature. The pressure P being equal to or less than the first pressure P1 is an example of a termination condition indicating that the refrigerant is in a predetermined state.

[0071] In step S130, the control unit 60 fully closes the expansion mechanism 24 and the shutoff valve 29, and then the process proceeds to step S140 (T2 in FIG. 4).

[0072] By fully closing the expansion mechanism 24 and the shutoff valve 29, the refrigerant recovered in the heat source heat exchanger 23 is prevented from returning to the user units 50 side.

[0073] In step S140, the control unit 60 determines whether a predetermined first time t1 has elapsed since the end of step S130, and proceeds to step S140 or step S150. Specifically, if the control unit 60 determines that the first time t1 has elapsed, the control unit 60 proceeds to step S140 (Yes), and if the first time t1 has not elapsed, the control unit 60 proceeds to step S150 (No). In other words, the control unit 60 repeats the process of step S140 until the first time t1 has elapsed. The first time t1 is, for example, approximately 20 to 30 seconds.

[0074] In step S150, the control unit 60 stops the motor 27a of the heat source fan 27, and ends the refrigerant recovery operation (T3 in FIG. 4).

[0075] By stopping the motor 27a of the heat source fan 27 after the second time t2 has elapsed since the expansion mechanism 24 and the shutoff valve 29 were fully closed, the refrigerant can be more reliably recovered to the heat source unit 20 side.

[0076] (3) Modifications (3-1) Modification A In step S120, the control unit 60 may determine whether the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first temperature, instead of whether the pressure P is equal to or lower than the first pressure P1. In other words, the termination condition for the refrigerant to be in a predetermined state may be that the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first temperature. The first temperature may be the outside air temperature (for example, a temperature that includes a predetermined margin above the outside air temperature).

[0077] In this case, the temperature of the refrigerant in the refrigerant circuit 10 may be detected by a temperature sensor (not shown) provided in the refrigerant circuit 10 .

[0078] (3-2) Modification B The pressure sensor 28 may be provided somewhere other than the gas pipe 10a, as long as it can detect the pressure of the refrigerant in the refrigerant circuit 10.

[0079] (3-3) Variation C The instruction to stop the heating operation may be an instruction to stop the heating operation (called thermo-off, etc.) that is output when the room temperature approaches the set temperature during the heating operation.

[0080] (4) Features (4-1) The refrigeration device 100 performs heating operation. The refrigeration device 100 includes a refrigerant circuit 10, a heat-source fan 27, and a control unit. The refrigerant circuit 10 has a compressor 21 and a heat-source heat exchanger 23. The heat-source fan 27 supplies air to the heat-source heat exchanger 23. The control unit 60 controls the compressor 21 and the heat-source fan 27. When the control unit 60 detects an instruction to stop the heating operation, it drives the heat-source fan 27 while keeping the compressor 21 stopped, and starts a refrigerant recovery operation in which refrigerant is recovered in the compressor 21 or the heat-source heat exchanger 23. When an end condition is met in which the refrigerant in the refrigerant circuit 10 is in a predetermined state, the control unit 60 stops the heat-source fan 27 and ends the refrigerant recovery operation.

[0081] By driving the heat source fan 27 to supply air to the heat source heat exchanger 23, the refrigerant in the heat source heat exchanger 23 is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit 10 is recovered into the heat source heat exchanger 23 from the utilization unit 50 side, which is at a relatively high pressure. Furthermore, the heat source fan 27 is stopped and the refrigerant recovery operation is terminated after an end condition is met in which the refrigerant in the refrigerant circuit 10 is in a predetermined state, so that the refrigerant recovery operation is prevented from being terminated before the refrigerant recovery has been fully completed. Therefore, the refrigeration system 100 can reliably recover refrigerant after operation is stopped.

[0082] (4-2) The termination condition is a state in which the pressure of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first pressure, or the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first temperature.

[0083] The refrigeration device 100 determines the state of refrigerant recovery based on the pressure or temperature of the refrigerant in the refrigerant circuit 10, and therefore can reliably recover refrigerant after operation is stopped.

[0084] (4-3) The termination condition is that the pressure of the refrigerant in the gas pipe 10a of the refrigerant circuit 10 is equal to or lower than a first pressure, or the temperature of the refrigerant in the gas pipe 10a of the refrigerant circuit 10 is equal to or lower than a predetermined first temperature.

[0085] The refrigeration device 100 determines the state of refrigerant recovery based on the pressure or temperature of the refrigerant in the refrigerant circuit 10, and therefore can reliably recover refrigerant after operation is stopped.

[0086] (4-4) The first temperature is equal to or lower than the outside air temperature.

[0087] The refrigeration device 100 determines the state of refrigerant recovery based on the temperature of the refrigerant in the refrigerant circuit 10, and therefore can reliably recover refrigerant after operation is stopped.

[0088] (4-5) The first pressure is the pressure of the refrigerant when the outside air temperature is the evaporation temperature.

[0089] The refrigeration device 100 determines the state of refrigerant recovery based on the pressure of the refrigerant in the refrigerant circuit 10, and therefore can reliably recover refrigerant after operation is stopped.

[0090] (4-6) During the refrigerant recovery operation, the control unit 60 rotates the heat source fan 27 at a speed equal to or higher than the minimum rotation speed during the heating operation.

[0091] Since the heat source fan 27 is rotated at a speed equal to or higher than the minimum speed in the heating operation, the condensation of the refrigerant is promoted. Therefore, the refrigeration apparatus 100 can reliably recover the refrigerant after the operation is stopped.

[0092] (4-7) The refrigerant circuit 10 further includes an expansion mechanism. The control unit 60 fully opens the expansion mechanism 24 during the refrigerant recovery operation.

[0093] Because the expansion mechanism 24 is fully opened, the expansion mechanism 24 is prevented from interfering with the flow of refrigerant from the utilization units 50 into the heat source heat exchanger 23. Therefore, the refrigeration apparatus 100 can reliably recover refrigerant after operation is stopped.

[0094] (4-8) When the control unit 60 detects the end condition in the refrigerant recovery operation, it stops the heat source fan 27 after a predetermined time has elapsed.

[0095] Since the heat source fan 27 continues to be driven even after the end condition is detected, the refrigeration device 100 can reliably recover the refrigerant after the operation is stopped.

[0096] (4-9) The refrigerant circuit 10 further includes a shutoff valve. The control unit 60 closes the gas-side shutoff valve before stopping the heat source fan 27 during the refrigerant recovery operation.

[0097] As a result, even if the temperature difference between the refrigerant in the utilization heat exchanger 51 and the refrigerant in the heat source heat exchanger 23 becomes small after the refrigerant recovery operation due to a drop in the temperature of the air-conditioned space, the refrigeration device 100 can prevent the refrigerant recovered in the heat source heat exchanger 23 from returning to the utilization unit 50.

[0098] (4-10) In the refrigerant recovery operation, the control unit 60 closes the shutoff valve 29 after detecting the end condition.

[0099] As a result, even if the temperature difference between the refrigerant in the utilization heat exchanger 51 and the refrigerant in the heat source heat exchanger 23 becomes small after the refrigerant recovery operation due to a drop in the temperature of the space to be air-conditioned, the refrigerant recovered in the heat source heat exchanger 23 is prevented from returning to the utilization unit 50.

[0100] (4-11) The instruction to stop the heating operation is an instruction that is output when the room temperature approaches the set temperature during the heating operation.

[0101] (4-12) The refrigerant is a flammable refrigerant.

[0102] This prevents the flammable refrigerant from leaking into the space to be air-conditioned after the refrigeration device 100 has stopped.

[0103] <Conclusion> Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the present disclosure as defined in the claims.

[0104] 10: Refrigerant circuit 10a: Gas pipe 21: Compressor 23: Heat source heat exchanger 24: Expansion mechanism 27: Heat source fan 29: Shutoff valve 60: Control unit 100: Refrigeration device P: Pressure P1: First pressure

[0105] Japanese Patent Application Laid-Open No. 2000-28210

Claims

1. A refrigeration system (100) that performs a heating operation, comprising: a refrigerant circuit (10) having a compressor (21) and a heat-source heat exchanger (23); a heat-source fan (27) that supplies air to the heat-source heat exchanger (23); and a control unit (60) that controls the compressor (21) and the heat-source fan (27), wherein, upon detecting an instruction to stop the heating operation, the control unit (60) drives the heat-source fan (27) while keeping the compressor (21) stopped, thereby starting a first operation in which refrigerant is recovered to the compressor (21) or the heat-source heat exchanger (23), and when an end condition that the refrigerant is in a predetermined state in the refrigerant circuit (10) is satisfied, the refrigeration system (100) stops the heat-source fan (27) and ends the first operation.

2. The refrigeration device (100) according to claim 1, wherein the termination condition is a state in which the pressure (P) of the refrigerant in the refrigerant circuit (10) is equal to or lower than a predetermined first pressure (P1), or the temperature of the refrigerant in the refrigerant circuit (10) is equal to or lower than a predetermined first temperature.

3. The refrigeration device (100) according to claim 2, wherein the termination condition is a state in which the pressure (P) of the refrigerant in the gas pipe (10a) of the refrigerant circuit (10) is equal to or lower than the first pressure (P1), or the temperature of the refrigerant in the gas pipe (10a) of the refrigerant circuit (10) is equal to or lower than the predetermined first temperature.

4. The refrigeration system (100) according to claim 2 or 3, wherein the first temperature is equal to or lower than an outside air temperature.

5. The refrigeration system (100) according to claim 2 or 3, wherein the first pressure (P1) is the pressure (P) of the refrigerant when the outside air temperature is at the evaporation temperature.

6. The refrigeration system (100) according to any one of claims 1 to 5, wherein the control unit (60) rotates the heat source fan (27) at a rotation speed equal to or higher than a minimum rotation speed in the heating operation in the first operation.

7. The refrigeration system (100) according to any one of claims 1 to 6, wherein the refrigerant circuit (10) further comprises an expansion mechanism (24), and the control unit (60) fully opens the expansion mechanism (24) in the first operation.

8. The refrigeration system (100) according to any one of claims 1 to 7, wherein the control unit (60) stops the heat source fan (27) after a predetermined time has elapsed when the termination condition is detected in the first operation.

9. The refrigeration system (100) according to any one of claims 1 to 8, wherein the refrigerant circuit (10) further comprises a shut-off valve (29), and the control unit (60) closes the shut-off valve (29) before stopping the heat source fan (27) in the first operation.

10. The refrigeration system (100) according to claim 9, wherein the control unit (60) closes the shutoff valve (29) after detecting the termination condition in the first operation.

11. The refrigeration device (100) according to any one of claims 1 to 10, wherein the instruction to stop the heating operation is an instruction that is output when the room temperature approaches a set temperature during the heating operation.

12. The refrigeration system (100) according to any one of claims 1 to 11, wherein the refrigerant is a flammable refrigerant.

Images